Bright Future: Jornada 720/680 CCFL to LED upgrade

Hi All!

Pleased to announce cheap boost inverter (per previous post link) fixed low brightness on battery with recent LED backlight upgrade... now no change in intensity if on 12volt AC or 8 volt battery power. Just need to shrink inverter to fit in case with LED driver and hook up dimmer circuit. IMO this is a major win!

Need to add dimmer mosfet circuit, but 'quick test' (connecting dim lead to ground for max dim) fully dims nicely for nighttime reading.

See photos below of battery powered Jornada in direct afternoon sunlight... please ignore camera artifacts. Yes, it's actually very readable in bright sunlight!! Something I've never seen before. Quite amazing.

Joval

Edited by joval 2022-03-09 12:59 AM








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It does look good!

I opened my 320 a couple of days ago... I can hardly read it inside now.. let alone outside ...

IMO, what I'm learning here should be applicable to most if not all H/Pc's including your 320 if an LED upgrade is desired.

Otherwise a simple ccfl swap with a new ccfl should be very easy and cheap to do, and the HP' 720 or 680 are designed for easy access/replacement (much more trouble as I recall with the MP900). I 'll bet the 320 is similarly easy to swap as Jornadas. Will look into it and report back. Another CESD to write up... ccfl replacement... easy peezy, IMO... must have!

I'm learning that the dc/dc boost converter may function as the LED driver alone, so separate LED driver board might not be required!! Needs overvoltage protection maybe. Will explore further... use Mosfet to dim or 555 timer for pwm. Undervoltage actually prolongs LED lifetime, overvoltage/current produces overheating shortens lifetime or worse.

Man oh man, the LED is so bright... really lights up a dark room. Brighter than my Samsung OLED tablet ! See below (with boost converter and LED driver board dangling on left side). Screen is brighter than shown due to camera artifact==> "rolling-dark-bar-overlying-screen effect " due to scan frequency difference, IMO. You Will be impressed!!

Joval







Edited by joval 2022-03-09 4:36 PM








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Problem is John, I have no idea about electronics. If I can manage not to blow something up, it's a good day

..............................................................Not to worry! I'll put together a tutorial "so easy, even a Cave-man can do it." BTW, turns out the boost-converter works alone so LED driver is not necessary.... makes things even cheaper and simpler. I'm closing in on the dimmer control to, a MosFET and bias resistor may do the trick. I must say LED with instant max brightness vs a dull slow warming up CCFL is a very welcomed improvement and should be extendable to the MP900/c as well. ................................................... joval on J720/WinCE +WRP/open-wifi to WPA2 via built in ESP8266/PIE4

Nice to know I'm not the only one here in whose hands a soldering iron is a deadly weapon.

I used to be able to solder like a boss... but designing a circuit and knowing where a mosfet, diode, etc were needed. Nope

Oh, Happy Day!!!

Great news==> The LED Uprade with Dimmer is now working fantastically well!! It dims down to almost complete darkness and brightens up so much you can read it in direct sunlight , in many more increments than the CCFL ever did.

And it's the cheapest upgrade you could ever imagine! No dedicated LED driver needed... and all easily powered by Jornada's internal CCFL power tab/ battery.

Here's what you need:

~6.25 inches of common LED strip (like this )
mini Boost converter set a 9 volts ( )
IRFZ44N logic level MOSFETs (need 2 of these) ( )
10K Ohm resistor 1/4 watt between Gate and Source
(Addendum: I forgot to list a 2N3904 transistor for constant current protection)

(the boost converter needs some trimming to fit into the Jornada... details to follow)

Amazingly simple and what a beautiful screen! Great contrast ratio, super dimmer dark.... to super daylight bright! Full details and schematic to follow (and future MP900 mod as well).

The only difference: The increase/decrease (alt [ and alt ] ) key functions are reversed==> right key now dims, left key now brightens. This baby is sure looking good.

Joval



Edited by joval 2022-03-31 2:24 AM

Hmmm... problem with above "reverse" keys is that when WinCE "dims the display" it actually leads to a "super-bright display"====> like prior to screen time-out or shutdown. So, I will reverse bias the Mosfet gate by adding a capacitor and a resistor... hope it's an easy fix.

Here is a great youtube video on "MOSFETs and How To Use Them" : https://www.youtube.com/watch?v=NK-CKtQuK20&t=910s . Really helped clear up any brain fog I had on the issue, and reminded me to use my breadboard instead of randomly soldering things only to fail, desolder, etc. Highly recommended for the curious.



Joval

Does the PCB fit inside the screen?
If not, we can design a custom PCB that replaces the CCFL converter board.

Stefan

Joval, this is very exciting and I am looking forward to replacing the failing backlight in my J720 and J728!!!

Thank you so much for sharing this :-)

Can't wait!

FYI... you're gonna love it.... bright daylight viewing anywhere. Did I mention Cheap, Cheap. Really easy to do IMO too. Superb contrast ratio , etc.

Yes, it is exciting!!!

Literally brings the J7xx out of the " dark ages." With Stefan's help we should be able to shrink the Mt3608 boost board so it fits... which is a minor issue, also control keys are reversed may require additonal pnp transistor ( if you want auto-screen dimming to work properly).

Contrary to my previous post, I now think battery life will be better (unless using outdoors).

Thanks for the feedback!

So.... No more living in the "Twilight Zone" ...and..." Next stop" : LED upgrade for the MP900/c... coming soon!

Joval

Edited by joval 2022-03-16 4:21 AM

Thanks for the help, Stefan! The MT3608 boost regulator board is about 5mm too wide, but a custom board would do the trick. All the components will easily fit in the in the ccfl board space. See my photo above labelled DirectAMSunlight.jpg. On the upper left there is the green LED driver board (no longer needed BTW) ==>it does fit width. In front of that you see the mt3608 board with the blue square variable resistor ==> too wide. The Mosfet will fit but is "overkill" rated at 50 Amps... no matter, won't require heat sink with that rating... it's not shown because the dimmer function wasn't set up yet in that photo.

Years ago I was a 'Fry Cook' at a Sizzler Steak house. Now I am a Fry Cook again... I trimmed the mt806 board down after removing the micro usb, inductor coil, and shottky diode using hot air soldering station, cutting the pcb with metal snips and resoldering. Each of several attempts failed cuz I "fried" the tiny mt3608 chip labelled (s35Baj0) as I am new at hot air soldering. : (

Not to worry, the mt3608 cost about $1.20 each... so I will keep trying.

SO.. yes a custom board should do the trick, and someone adept at soldering the components ... hint, hint ( which are really cheap online) is surely welcomed.

I'm still working on the control reversal issue... but that is icing on the cake... everything works astoundly well as is except auto-dimming.

Have at it Herr Maestro!

Sharing is Caring,

Joval


Edited by joval 2022-03-16 4:15 AM

I just reviewed the MT3608 data sheet and circuit, so I understand circuit design. IMO, a longer narrower board that fits J720 would actually be much simpler layout and should be easy to design, per your suggestion. Even I should be able to do it!!

https://datasheetspdf.com/pdf/909246/AEROSEMI/MT3608/1

Joval

Edited by joval 2022-03-17 2:45 PM

Just ordered these... may be a better fit as the others are too big which is proving troublesome to downsize. 9 volts not quite so bright as 9.3 to 9.6 ideal.

Will need resistor and maybe inductor swap to 22uH from 3.3 uH change to increase input voltage from 5v to 12v, and give 9.6v out though... per mt3608 data sheet mentioned above. Thinking : canabalize from the bigger device if bigger inductor needed



Quite a bit of mt3608 chip carnage so far... but I'm learning how to use heat gun to solder smd items. So have lots of "spare parts" for inductor swap, etc. , on smaller board ( which can serve as a model for a custom board perhaps).

Busy keeping the lights on... LED so superior to Ccfl ... can dim down to dark is impossible with Ccfl! Bright enough for outdoor as well.

Joval

Edited by joval 2022-03-19 4:12 PM